Preparation of stable non-pyrophoric alkyllithium compositions



United Our invention relates to the preparation of stable nonpyrophoric alkyllithium compositions.

Alkyllithium compounds as, for example, n-butyllithiurn, represent a class of known compounds. They are conventionally prepared in the form of solutions in normally liquid hydrocarbons such as n-pent-ane and n-hexane. In this form, the alkyllithium compounds possess a number of serious disadvantages with reference to their handling and use. Chief among these disadvantages are the pyrophoricity and the lack of stability of such alkyllithium solutions upon exposure to air and moisture. Because of these characteristics of such heretofore known alkyllithium compositions, special handling, packaging and shipping procedures have been required. This has militated strongly against efforts to develop significant commercial uses for the alkyllithium compounds.

Our invention is predicated upon certain discoveries which enable the production of alkyllithium compositions in the form of stable and non-pyrophoric mixtures containing substantial proportions of the alkyllithium compounds. We have found that if the aikyllithium compounds are embodied or incorporated in inert hydrocarbons or mixtures of hydrocarbons which are solid or semisolid rat ordinary room temperatures, the resulting compositions are non-pyrophoric and stable in the presence of air and moisture. The novel 'alkyl-lithium com positions of our invention, thus, lend themselves to relatively easy and convenient handling and shipping thereof is greatly facilitated not only from the standpoint of lower costs of shipping containers but, also, from the standpoint of substantial elimination of hazardous shipping problems.

The inert hydrocarbons which are solid or semi-solid at room temperatures which we have found to be especially satisfactory for use in the practice of our invention comprise paraffin waxes and petrolatums as well as mixtures of paraffin waxes and pet-rolatums in various proportions. The paraffin waxes advantageously utilized are those which have melting points in the range of approximately 100 degrees F. to 200 degrees F.

The alkyllithium content of the composition of our invention is variable and will usually range in amount up to about 50 weight percent. Particularly satisfactory are those compositions in which the weight percent of the alkyllithium will fall within the range of about to about percent with 20 percent representing a good average.

We have found that the novel compositions of our invention may be prepared in a variety of ways. Illustrative procedures which we have found to be satisfactory may be outlined broadly as follows:

(1) By the direct preparation of the alkyllithium compound in the molten normally solid or semi-solid inert hydrocarbon or hydrocarbon mixture followed by separation of the aforesaid alkyllithium-molten inert hydrocarbon from the lithium halide by-product followed by solidification of the alkyllithium-molten inert hydrocarbon.

(2) By initially preparing the alkyl-lithium compound in a solution of a light hydrocarbon solvent such as pentane or hexane, for instance, in accordance with heretofore known prior art methods, after which the inert normally solid or semi-solid hydrocarbon or hydrocarbon mixture is added either in previously melted form or which, after addition, is heated to its melting temperature,

atent "ice 2 and then stripping off the pentane or hexane under a vacuum, after which the \IILIXIUJTB is cooled to allow the normally solid or semi-solid inert hydrocarbon to solidify.

(3) By a combination of the procedures described in the above paragraphs (1) and (2), namely, by preparing the alkyllithium compound in a light hydrocarbon solution, for example, a pentane or hexane solution, of the normally solid or semi-solid inert hydrocarbon or hydrocarbon mixture, after which the desired product is separated from the lithium halide by-product and the light hydrocarbon solvent, such as pentane or hexane, is stripped off under a vacuum.

In those cases where the procedures described above under (2) and (3) are employed, various light hydrocarbons other than peutane and hexane can be utilized. In general, such light hydrocarbons comprise straight chain and branched chain hydrocarbons in the range of C T-I to C H additional examples of which are n-heptame and n-octane, as well as mixtures thereof, petroleum ether, aromatic solvents such as benzene, toluene and xylene, and mixtures of aromatic and parafiinic solvents such as lactol spirits or mineral spirits.

The following example is illustrative of one suitable procedure for the preparation of the novel alkyllithium compositions of the present invention. It will be understood that various changes may be made with reference to the selection of particular normally solid or semi-solid inert hydrocarbons, proportions of ingredients, and various details of procedure without in any way departing from the principles of the invention in view of the guiding teachings provided herein.

Example PREPARATION OF A n-BUTYLLITHIUM-PARAFFIN WAX MIXTURE CONTAINING 20 WEIGHT PERCENT OF n-BUTYLLITHIUM, AND USING A WAX COMPOSITION OF 10% PETROLATUM AND PARAFFIN WAX A mixture of 76.3 grams of a paraffin wax (MP. 132 degrees F.) and 8.5 grams of white petnolatum was melted and charged into a 500 ml. round-bottom flask, fitted with a vacuum connection, an enclosed magnetic stirrer, and an argon flushed, graduated dropping funnel. The dropping funnel contained 130 ml. of a 2.75 molar solution of n-butyllithium in n-hexane, which was then added to the molten wax mixture, after which the funnel was removed and replaced with an adapter and thermometer. The mixture in the flask was heated to 65 degrees C., followed by application of vacuum. Hexane was distilled off and condensed. The initial vacuum of 130 mm. was slowly reduced to 4 mm. All hexane was removed in 20 minutes. Argon was bled into the system to atmospheric pressure. The molten mixture was poured into a cylindrical steel mold (to provide a 10" stick) which had been placed in a container continuously flushed with argon. After cooling and solidification in the argon atmosphere, the 10" stick was removed from the mold.

The stick was handled freely in the air, without the usual protective measures necessary with hexane or like light liquid hydrocarbon solutions of n-butyllithium. The n-butyllithium content of various sections of the stick was determined by chemical analysis with the following results.

a. A transverse center cut: Wt. Percent Active alkyl 20.8 Total base 22.4

b. A transverse cut from top of rod:

Active alkyl 20.8 Total base 22.3

c. A transverse cut from bottom of rod:

Active alkyl 20.8 Total base 22.1

The above analyses show the excellent uniformity achieved.

A sample of the composition of the above example was tested for pyrophoricity by melting in air and pouring on moist cotton. There was a slight reaction but no fire or charring of the moist cotton. This is in sharp contrast to the fire and charring of moist cotton which occurs when a solution of n-butyllithium in heptane or hexane is poured on moist cotton. Another sample of the composition produced in accordance with the above example was squeezed between moist filter paper. Again, there was. slight reaction but no fire or charring of the moist filter paper, a result also in sharp contrast with that which occurs when a similar experiment is carried out with heptane or hexane solution of n-butyllithium. A further test, in which a. sample of the product produced in accordance with the above example was explosed at 42 degrees C. in a 100% relative humidity atmossphere for 1 hour, showed outstanding stability under such adverse conditions, the loss of active alkyl concentration being less than 2%.

While the invention is particularly applicable to the preparation of stable non-pyrophoric compositions in which the alkyllithium compound is n-butyllithium, other alkyllithium compounds can also be utilized to produce stable non-pyrophoric compositions as, for example, sec-butyllithium, tert-butyllithium, amyllithium, and, in general, those alkyllithium compounds which are soluble or readily dissolvable in hydrocarbon media. The novel teachings of the present invention can also be utilized to provide stable non-pyrophoric compositions containing aryllithium compounds such as phenyllithium but it has its greatest utility, as indicated, in the production of alkyllithium compounds, notably n-butyllithium and other butyllithium compounds.

What we claim as new and desire to protect by Letters Patent of the United States is;

1. A new and useful, composition of matter which is semi-solid to solid at room temperature comprising (a) at least one semi-solid to solid hydrocarbon selected from the group consisting of petrola-tums and of paratfin waxes, and (b) an alkyllithium, said alkyllithium being generally uniformly distributed throughout said semisolid to solid hydrocarbon.

2. A new and useful composition of matter which is ing from about 15 to about semi-solid to solid at room temperature comprising (a) at least one semi-solid to solid hydrocarbon selected from the group consisting of petrolatums and parailiin waxes, said paraflin waxes having melting points within the range of 100 to 200 degrees F, and (b) an alkyllithium, said alkyllithium being generally uniformly distributed throughout said semi-solid to solid hydrocarbon, said composition containing up to about weight percent of said alkyllithium.

3. A new and useful composition of matter which is semi-solid to solid at room temperature comprising (a) a mixture of at least one paraffin wax and petrolatum, said parafiin wax predominating substantially over that of the petrolatum, said parafiin wax having a melting point in the range of to 200 degrees F., and (b) an alkyllithium, said a-lkyllithium being generally uniformly distributedjthroughout said semi-solid to solid mixture of parafiin wax and petrolatum, said composition contain- 25 weight percent of said alkyllithium.

4. A new and useful composition of matter which is semi-solid to solid at room temperature comprising (a) a mixture of parafiin wax and petrolatum in which the parafiin wax predominates substantially over that of the petrolatum, and (b) butyllithium, said butyllithium being generally uniformly distributed throughout said semisolid to solid mixture of parailin wax and petrolatum, said composition containing from about 15 to about 50 weight percent of said butyllithium.

5. A new and useful composition of matter which is semi-solid to solid at room temperature comprising (a) .at least one semi-solid to solid hydrocarbon selected from the group consisting of petrolatums and of paraflin waxes, and (b) an aryllithium, said aryllithium being generally uniformly distributed throughout said semisolid to solid hydrocarbon.

References Cited inthe file of this patent Coates: Organo-Metallic Compounds, The Alkali Metals, 2nd edition, 1960, John Wiley and Sons, Inc., New York City, New York, pages 1-42, page 7 specifically cited. 

1. A NEW AND USEFUL COMPOSITION OF MATTER WHICH IS SEMI-SOLID TO SOLID AT ROOM TEMPERATURE COMPRISING (A) AT LEAST ONE SEMI-SOLID TO SOLID HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF PETROLATUMS AND OF PARAFFIN WAXES, AND (B) AN ALKYLLITHIUM, SAID ALKYLLITHIUM BEING GENERALLY UNIFORMLY DISTRIBUTED THROUGHOUT SAID SEMISOLID TO SOLID HYDROCARBON. 